Compared with the liquid crystal panel, an OLED in the active matrix light emitting diode (Active Matrix/Organic Light Emitting Diode, AMOLED) panel is self-luminous, rather than using a backlight. The fabrication of the OLED includes evaporating an organic material onto an array substrate, and an evaporation mask is used in evaporating the organic material. Typically, the evaporation mask is welded onto the frame and then is placed in an evaporation chamber. Such structure of welding the evaporation mask and the frame together is called a mask frame assembly (MFA).
However, edges of the evaporation mask may tend to be curled up in the evaporation process, due to heat, magnetic force or other influencing factors, which affects the flatness of the evaporation mask, and finally causes shadow to be formed on a pattern evaporated onto the glass, thereby affecting evaporation effect.